The olive tree is an evergreen tree or shrub native to the Mediterranean, Asia and Africa. It is short and squat, and rarely exceeds 8–15 metres (26–49 ft) in height. The silvery green leaves are oblong in shape, measuring 4–10 centimetres (1.6–3.9 in) long and 1–3 centimetres (0.39–1.2 in) wide. The trunk is typically gnarled and twisted.

The fruit is a small drupe 1–2.5 centimetres (0.39–0.98 in) long, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested at the green stage (green olives) or left to ripen to a rich purple colour (black olives). Canned black olives may contain chemicals that turn them black artificially.